This invention is in the field of impact print heads magnetically actuated, wherein the character bearing members are permanently magnetically magnetized, and the characters are electronically selected.
Print heads are normally part of a typewriter carriage, so that when the head is actuated and a character is selected and printed the carriage is advanced to the next position for imprinting the next character.
The prior art uses print heads that are generally massive and have high inertia moments thereby slowing down the printing speed.
Other disadvantages of the prior art is that it is not possible to read the last few characters printed due to the print means causing visual obstruction.
Also existing in the prior art is a mechanically actuated print wheel, the character elements of which are activated only by an armature of a solenoid striking them. This wheel is made of metal such as steel for obtaining resiliency and is substantially heavier than any of the wheels of the instant invention due to support needed for the character elements and hence the use of relatively thick metal. The result is a much slower print action due to greater built-in inertia moments. Such prior art wheel resembles a typical wagon wheel structure except that there is no outer rim present and the spokes of the wheel each have a character at their extremities. This wheel, its spokes or that portion bearing the character is not permanently magnetized and therefore has the disadvantage of not being magnetically impelled to print the character. Such wheel may be found in typewriters identified as Model HyType I licensed for fabrication by Diablo Systems, Inc. of Hayward, California to Lexitron Corporation and used in its typewriter system made under Model Videotype 92.
U.S. Pat. No. 3,842,960 issued to the same inventive entity, although overcoming some of the prior art disadvantages has print wheels which have magnetizable members radially positioned on the disk or in the flat cylinder retaining the print character bearing members, and these magnetizable members add a good deal of mass to the wheel slowing it down and making rapid stopping and starting of the stepping motor difficult. Additionally, the disk or flattened cylinder is so constructed so as to have the character face oriented orthogonally to the plane of the disk or flattened cylinder. This orientation, sets up the requirement for the magnetizable radial members to be large in size in order to hold the character bearing members when the disk is being rotated at high speed, since in these structures the character bearing members have to be rather massive.